This invention relates to an automatic spike driver for driving spikes through holes in rail tie plates to secure rails to rail ties.
A tie plate is a channelled plate which rests on a wooden tie and which receives a rail. The tie plate has two holes on each side but normally spikes are driven through only one hole on each side into the tie, the head of the spike bearing against or being slightly spaced from the rail to ensure the rail, tie plate and tie are all secured together. A problem in driving the spikes automatically is that the holes must be accurately located automatically and a spike setter and driver head positioned so that the spikes can be driven accurately through the holes. Another problem is that the spikes have to be conveyed to the drive head in the correct orientation with respect to the rail.
U.S. Pat. No. 3,753,404 to Bryan discloses a spike driver in which rail locators are swung inwardly by an operating cylinder until they engage the rail and these establish a reference for the holes in the tie plate in the X-direction, i.e., in the direction laterally of the rails. The Bryan device then sweeps in the Y direction, i.e., along the rail until a hole is detected at which point a spike is driven by a drive head through the hole into the tie.
One problem with the prior device is that it is not easy to envisage how the device would cope with different thicknesses of rails as there is no disclosure as to what causes the operating cylinder to stop extending and one must assume that the piston continues to the end of its stroke.
Moreover the angle at which a spike is driven would vary with different thicknesses of rail thus limiting the use of the prior machine.
Another problem of the earlier device is that it uses a flexible tube system to convey spikes from a hopper directly to the drive head and so the geometry of this guide tube changes according to the distance the drive head moves in the X and Y directions. Such a variable geometry arrangement is likely, in practice, to give rise to spike feed, and particularly, spike orientation problems.